Read this if you want to attract great Physics marks!
Are you struggling with Electromagnetism for HSC Physics? Don’t worry, in this article, we’ll explain the key concepts you need to know to fulfil the NESA Physics Outcomes.
Year 12 Physics students find the Electromagnetism module conceptually challenging. As such, students struggle to provide scientific responses that are logical and sequential as required to obtain full marks in exam questions. In Part 2 of our HSC Physics study guide, the Matrix Science Team explains the key concepts in this topic using flowcharts to simplify complex processes.
Some flowcharts from the Matrix Year Physics Theory Book are provided below to help you write better scientific responses. If you missed it, don’t forget to have a look at Part 1 of the HSC Physics study guide on Advanced Mechanics.
The motor effect is a phenomenon where a current carrying conductor within a magnetic field experiences a force. Although it may not look like it at first glance, this motor effect is actually a consequence of the Lorentz force:
The most famous application of the motor effect is the operation of a DC Motor, something students must learn to explain in this module. The trick to understanding the DC Motor is to realise there are two key components: the motor effect producing a torque, and the split-ring commutator allowing continuous rotation in the same direction. This is shown in the flowchart below:
Students learn about Faraday’s Law which explains how electric potential differences (voltages) and currents can be generated. One of the more common examples involves a moving conductor in a magnetic field, a phenomenon which is once again derived from the Lorentz force:
Faraday’s Law informs us of the circumstances under which an EMF and current are induced, and Lenz’s Law outlines the direction of the induced current. They are often grouped together when explaining the response of a circuit to a change in magnetic flux:
A useful implementation of Faraday’s and Lenz’s laws is electromagnetic braking, which uses induced currents to slow the motion of a metal wheel. The process is explained below – crucially this involves no physical contact between the brake and the wheel.
A second device that uses Faraday’s and Lenz’s laws is the induction motor, which uses induced eddy currents to produce motion of the rotor without the need for slip rings/split ring commutator. The process of inducing rotation is outlined below:
The principle of electromagnetic induction is also used to generate electricity via an electric generator. In some aspects, these function in the opposite way to motors: a torque is applied to the rotor, and an alternating current is extracted. The process is outlined in the flowchart below:
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